1. Related Applications
The present application is based on, and claims priority from, Taiwan Application Ser. No. 93125029, filed Aug. 19, 2004, the disclosure of which is hereby incorporated by reference herein in its entirety.
2. Field of Invention
The invention pertains to an encoder signal compensation method and the apparatus thereof. In particular, it relates to a compensation method for the encoder signals of printing apparatuses and the printing apparatus thereof.
3. Related Art
With the rapid development in the electronic industry, printing apparatuses such as copiers and printers have been widely used in daily life. Besides large companies, copiers and laser printers are already popular in various kinds of places, including families. The operations of copiers and laser printers rely on opto-electronic image printing techniques. Advanced opto-electronic image printing techniques enables manufacturers to satisfy the requirements of high-quality laser printing and the SOHO market.
The uses of color computer multimedia further increase needs in color copiers and printers. Laser printers employs complicated opto-electronic image printing configuration and procedure to form images on an output medium. The standard opto-electronic image printing procedure includes seven basic steps: charging, exposing, developing, transferring, fusing, cleaning, and erasing. The standard color printing of color printers further involves four different colors of toners: yellow, magenta, cyan, and black.
In order to increase the resolution of color laser printers, the resolution of the encoder and code strip have to be increased too. With a quadrature encoder, the resolution of a color printer can readily reach 1,200 DPI, 2,400 DPI, or higher. However, when reading signals using the quadrature encoder, the errors in the packaging precision of the encoder, the installation of the encoder, and the mechanical precision of the printer will all result in errors in the encoder signals.
The errors of a conventional quadrature encoder can be classified into phase errors and width errors. With reference to FIG. 1, the phase error and the width error of an encoder signal are illustrated. When the signal obtained by CH. A is as the solid wave 110 and that obtained by CH. B is as the solid wave 120, the quadrature signal obtained from the decoder will be as the solid wave 130. The high-level wave 112 of the solid wave 110 and the width of the low-level wave 114 are different because of the width error 140. The solid wave 110 of CH. A and the solid wave 120 of CH. B further have the phase error 150 due to the existence of a phase different. As both the width error 140 and the phase error 150 exist, the encoder produces quadrature rectangular waves with unequal widths as in the solid wave 130. This will result in high frequency banding when the printer prints, rendering a low picture quality.
Therefore, how to effectively avoiding the high frequency banding of the printer to increase the printing quality of printers and copier is what both manufacturers and users are looking for.